02.MyBatis配置文件详解

mysql.driver = com.mysql.jdbc.Driver
mysql.url = jdbc:mysql://localhost:3306/test
mysql.username = root
mysql.password = lizhiwei
oracle.driver=oracle.jdbc.driver.OracleDriver
oracle.url=jdbc:oracle:thin:@127.0.0.1:1521:orcl
oracle.username=
oracle.password=

<properties resource="config.properties">
    <property name="property_0" value="value_1" />
    <property name="property_2" value="value_2" />
</properties>
<environments default="development">
    <environment id="development">
        <transactionManager type="JDBC" />
        <dataSource type="POOLED">
            <property name="driver" value="${mysql.driver}" />
            <property name="url" value="${mysql.url}" />
            <property name="username" value="${mysql.username}" />
            <property name="password" value="${mysql.password}" />
        </dataSource>
    </environment>
</environments>

SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader, props);
// ... or ...
SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader, environment, props);

1. 在 properties元素体内指定的属性首先被读取。
   
2. 然后根据properties元素中的resource属性读取类路径下属性文件或根据url属性指定的路径读取属性文件，并覆盖已读取的同名属性。
   
3. 最后读取作为方法参数传递的属性，并覆盖已读取的同名属性。

<settings>
    <setting name="cacheEnabled" value="true" />
    <setting name="lazyLoadingEnabled" value="true" />
    <setting name="multipleResultSetsEnabled" value="true" />
    <setting name="useColumnLabel" value="true" />
    <setting name="useGeneratedKeys" value="false" />
    <setting name="autoMappingBehavior" value="PARTIAL" />
    <setting name="defaultExecutorType" value="SIMPLE" />
    <setting name="defaultStatementTimeout" value="25" />
    <setting name="defaultFetchSize" value="100" />
    <setting name="safeRowBoundsEnabled" value="false" />
    <setting name="mapUnderscoreToCamelCase" value="false" />
    <setting name="localCacheScope" value="SESSION" />
    <setting name="jdbcTypeForNull" value="OTHER" />
    <setting name="lazyLoadTriggerMethods" value="equals,clone,hashCode,toString" />
</settings>

<typeAliases>
	<typeAlias alias="Author" type="domain.blog.Author" />
	<typeAlias alias="Blog" type="domain.blog.Blog" />
	<typeAlias alias="Comment" type="domain.blog.Comment" />
	<typeAlias alias="Section" type="domain.blog.Section" />
</typeAliases>

<typeAliases>
	<package name="domain.blog" />
</typeAliases>

@Alias("author")
public class Author {
    ...
}

别名          映射的类型
_byte           byte
_long           long
_short          short
_int            int
_integer        int
_double         double
_float          float
_boolean        boolean
string          String
byte            Byte
long            Long
short           Short
int             Integer
integer         Integer
double          Double
float           Float
boolean         Boolean
date            Date
decimal         BigDecimal
bigdecimal      BigDecimal
object          Object
map             Map
hashmap         HashMap
list            List
arraylist       ArrayList
collection      Collection
iterator        Iterator 

@MappedJdbcTypes(JdbcType.VARCHAR)
public class ExampleTypeHandler extends BaseTypeHandler<String>
{
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, String parameter, JdbcType jdbcType) throws SQLException
    {
        ps.setString(i, parameter);
    }
    @Override
    public String getNullableResult(ResultSet rs, String columnName) throws SQLException
    {
        return rs.getString(columnName);
    }
    @Override
    public String getNullableResult(ResultSet rs, int columnIndex) throws SQLException
    {
        return rs.getString(columnIndex);
    }
    @Override
    public String getNullableResult(CallableStatement cs, int columnIndex) throws SQLException
    {
        return cs.getString(columnIndex);
    }
}

<typeHandlers>
	<typeHandler handler="org.mybatis.example.ExampleTypeHandler" />
</typeHandlers>

public class GenericTypeHandler<E extends MyObject> extends BaseTypeHandler<E> {
  private Class<E> type;
  public GenericTypeHandler(Class<E> type) {
    if (type == null) throw new IllegalArgumentException("Type argument cannot be null");
    this.type = type;
  }
  ...

<!-- mybatis-config.xml -->
<typeHandlers>
	<typeHandler handler="org.apache.ibatis.type.EnumOrdinalTypeHandler" javaType="java.math.RoundingMode" />
</typeHandlers>

<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="org.apache.ibatis.submitted.rounding.Mapper">
	<resultMap type="org.apache.ibatis.submitted.rounding.User" id="usermap">
		<id column="id" property="id"/>
		<result column="name" property="name"/>
		<result column="funkyNumber" property="funkyNumber"/>
		<result column="roundingMode" property="roundingMode"/>
	</resultMap>
	<select id="getUser" resultMap="usermap">
		select * from users
	</select>
	<insert id="insert">
	    insert into users (id, name, funkyNumber, roundingMode) values (
	    	#{id}, #{name}, #{funkyNumber}, #{roundingMode}
	    )
	</insert>
	
	<resultMap type="org.apache.ibatis.submitted.rounding.User" id="usermap2">
		<id column="id" property="id"/>
		<result column="name" property="name"/>
		<result column="funkyNumber" property="funkyNumber"/>
		<result column="roundingMode" property="roundingMode" typeHandler="org.apache.ibatis.type.EnumTypeHandler"/>
	</resultMap>
	<select id="getUser2" resultMap="usermap2">
		select * from users2
	</select>
	<insert id="insert2">
	    insert into users2 (id, name, funkyNumber, roundingMode) values (
	    	#{id}, #{name}, #{funkyNumber}, #{roundingMode, typeHandler=org.apache.ibatis.type.EnumTypeHandler}
	    )
	</insert>
</mapper>

<!-- mybatis-config.xml -->
<objectFactory type="org.mybatis.example.ExampleObjectFactory">
    <property name="someProperty" value="100"/>
</objectFactory>

1. Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)
   
2. ParameterHandler (getParameterObject, setParameters)
3. ResultSetHandler (handleResultSets, handleOutputParameters)
4. StatementHandler (prepare, parameterize, batch, update, query)

// ExamplePlugin.java
@Intercepts({ @Signature(type = Executor.class, method = "update", args = { MappedStatement.class, Object.class }) })
public class ExamplePlugin implements Interceptor
{
    public Object intercept(Invocation invocation) throws Throwable
    {
        return invocation.proceed();
    }
    public Object plugin(Object target)
    {
        return Plugin.wrap(target, this);
    }
    public void setProperties(Properties properties)
    {
    }
}

<!-- mybatis-config.xml -->
<plugins>
	<plugin interceptor="org.mybatis.example.ExamplePlugin">
		<property name="someProperty" value="100" />
	</plugin>
</plugins>

SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader, environment);
SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader, environment,properties);

SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader);
SqlSessionFactory factory = sqlSessionFactoryBuilder.build(reader,properties);

<environments default="development">
	<environment id="development">
		<transactionManager type="JDBC">
			<property name="..." value="..." />
		</transactionManager>
		<dataSource type="POOLED">
			<property name="driver" value="${driver}" />
			<property name="url" value="${url}" />
			<property name="username" value="${username}" />
			<property name="password" value="${password}" />
		</dataSource>
	</environment>
</environments>

1. 默认的环境 ID（比如:default="development"）。
   
2. 每个 environment 元素定义的环境 ID（比如:id="development"）。
3. 事务管理器的配置（比如:type="JDBC"）。
4. 数据源的配置（比如:type="POOLED"）。

1. JDBC – 这个配置就是直接使用了 JDBC 的提交和回滚设置，它依赖于从数据源得到的连接来管理事务范围。
   
2. MANAGED – 这个配置几乎没做什么。它从来不提交或回滚一个连接，而是让容器来管理事务的整个生命周期（比如 JEE 应用服务器的上下文）。 默认情况下它会关闭连接，然而一些容器并不希望这样，因此需要将 closeConnection 属性设置为 false 来阻止它默认的关闭行为。例如: 
   

public interface TransactionFactory
{
    void setProperties(Properties props);
    Transaction newTransaction(Connection conn);
    Transaction newTransaction(DataSource dataSource, TransactionIsolationLevel level, boolean autoCommit);
}

public interface Transaction
{
    Connection getConnection() throws SQLException;
    void commit() throws SQLException;
    void rollback() throws SQLException;
    void close() throws SQLException;
}

1. driver – 这是 JDBC 驱动的 Java 类的完全限定名（并不是JDBC驱动中可能包含的数据源类）。
   
2. url – 这是数据库的 JDBC URL 地址。
3. username – 登录数据库的用户名。
4. password – 登录数据库的密码。
5. defaultTransactionIsolationLevel – 默认的连接事务隔离级别。